JP2005265587A - Torque detection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque detection apparatus, having little stresses or distortions which occur in a flux-concentrating ring and is capable of facilitating assembling. <P>SOLUTION: The torque detection apparatus is provided with a first shaft 1 and a second shaft 2 connected to each other by a connecting shaft 3; a permanent magnet 5 fixed to the first shaft 1; a plurality of soft magnetic bodies 4a and 4b fixed to the second shaft 2 and arranged in a magnetic field of the permanent magnet 5 to form a magnetic circuit; a plurality of auxiliary soft magnetic bodies 8, magnetically coupled with the soft magnetic bodies 4a and 4b for inducing magnetic flux from the soft magnetic bodies 4a and 4b, and a detector 6 for detecting the magnetic flux induced by the auxiliary soft magnetic bodies 8. The plurality of the auxiliary soft magnetic bodies 8 and the detector 6 are molded by a synthetic resin 28 into a single piece. When a torque is added to the first shaft 1 or the second shaft 2, the torque is detected on the basis of output of the detector 6 in the torque detection apparatus. The synthetic resin 28 is provided with a plurality of holes 18, and stresses which are generated in the auxiliary soft magnetic bodies 8 by molding are reduced by the holes 18. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is suitably used for an electric power steering device of a vehicle, and the like. The first shaft and the second shaft are coaxially connected by a connecting shaft, the permanent magnet fixed to the first shaft, and the second shaft. A plurality of soft magnetic bodies fixed and arranged in a magnetic field of a permanent magnet to form a magnetic circuit; a plurality of auxiliary soft magnetic bodies magnetically coupled to the soft magnetic bodies to induce magnetic flux from the soft magnetic bodies; and an auxiliary The present invention relates to a torque detection device that detects a magnetic flux based on an output of a detector when a torque is applied to a first shaft or a second shaft. .

  As a vehicle steering apparatus, there is an electric power steering apparatus that assists steering by driving an electric motor to reduce a burden on a driver. This includes an input shaft connected to a steering member (steering wheel, steering wheel), an output shaft connected to a steering wheel by a pinion, a rack, and the like, and a connecting shaft that connects the input shaft and the output shaft. The torque detection device detects the steering torque applied to the input shaft based on the angle, and drives and controls the steering assist electric motor linked to the output shaft based on the detected steering torque value. Conventionally, a magnetic detection resolver that detects a rotational position using a coil, an optical encoder detection device that detects transmission of light, or the like is used as a torque detection device of such an electric power steering device.

  Further, in Patent Document 1, as shown in an exploded perspective view (a), a longitudinal sectional view (b) and a transverse sectional view (c) of FIG. The shaft 2, the ring-shaped 24-pole permanent magnet 5 fixed to the input shaft 1, and a plurality of soft magnetic bodies fixed to the output shaft 2 and arranged in the magnetic field of the permanent magnet 5 to form a magnetic circuit 4a and 4b, two magnetic flux collecting rings 8 and 8 which are magnetically coupled to the magnetic yokes 4a and 4b and induce magnetic flux from the magnetic yokes 4a and 4b, and magnetic flux induced by the magnetic collecting rings 8 and 8 Two magnetic sensors 6 and 6 (Hall IC) for detecting the torque are proposed, and when torque is applied to the input shaft 1, a torque sensor for detecting torque is proposed based on the output of the magnetic sensors 6 and 6. Yes.

Further, as shown in FIG. 1, the present applicant uses the above-described torque sensor to integrally mold the magnetic yokes 4a and 4b with the synthetic resin 24 to synthesize the magnetic flux collecting rings 8 and 8 with the magnetic sensors 6 and 6. Japanese Patent Application No. 2003-332511 proposes a torque sensor that is molded integrally with resin 28 to facilitate assembly.
JP 2003-149062 A

  In the torque sensor proposed in Japanese Patent Application No. 2003-332511, since the magnetism collecting rings 8 and 8 are molded with synthetic resin, stress and strain are applied to the magnetism collecting rings 8 and 8 due to volume change when the synthetic resin is cured. Occurs. Permalloy (nickel-iron alloy) is used for the magnetism collecting rings 8 and 8, but the magnetic properties of permalloy are sensitive to stress and strain, and as shown in FIG. The permeability is reduced and the coercive force is increased. Therefore, there is a problem that the magnetic flux detected by the magnetic sensors 6 and 6 changes and the torque value cannot be detected accurately.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a torque detection device with small stress and distortion generated in a magnetism collecting ring.

  A torque detection device according to a first aspect of the present invention includes a first shaft and a second shaft that are coaxially connected by a connection shaft, a permanent magnet fixed to the first shaft, a fixed to the second shaft, and the permanent shaft A plurality of soft magnetic bodies arranged in a magnetic field of the magnet to form a magnetic circuit; a plurality of auxiliary soft magnetic bodies magnetically coupled to the soft magnetic body for inducing magnetic flux from the soft magnetic bodies; and A detector for detecting a magnetic flux induced by the magnetic body, and the plurality of auxiliary soft magnetic bodies and the detector are molded and integrated with synthetic resin, and torque is applied to the first shaft or the second shaft. A torque detecting device adapted to detect the torque based on the output of the detector, wherein the synthetic resin has a plurality of holes and generates stress generated in the auxiliary soft magnetic body by a mold. , Characterized by being reduced by the hole

  A torque detection device according to a second aspect of the present invention includes a first shaft and a second shaft that are coaxially coupled by a coupling shaft, a permanent magnet fixed to the first shaft, a fixed to the second shaft, and the permanent shaft A plurality of soft magnetic bodies arranged in a magnetic field of the magnet to form a magnetic circuit; a plurality of auxiliary soft magnetic bodies magnetically coupled to the soft magnetic body for inducing magnetic flux from the soft magnetic bodies; and A detector for detecting the magnetic flux induced by the magnetic body, and when the torque is applied to the first shaft or the second shaft, the torque is to be detected based on the output of the detector. The detection device includes a case made of a synthetic resin for housing the auxiliary soft magnetic body and the detector, the auxiliary soft magnetic body has elasticity, and the auxiliary soft magnetic body is expanded and contracted by the elasticity and fitted into the case. It is characterized by that.

  According to the torque detector of the first invention, the stress and strain generated in the auxiliary soft magnetic material are reduced, the deterioration of the magnetic properties (magnetic permeability, coercivity) of the auxiliary soft magnetic material is reduced, and the permeability is reduced. The sensor sensitivity is improved, the increase in coercive force is reduced, and the hysteresis (history phenomenon) can be reduced. Moreover, since the amount of synthetic resin can be reduced, weight reduction and part cost reduction can be achieved.

  According to the torque detector of the second invention, the stress and strain generated in the auxiliary soft magnetic material are reduced, the deterioration of the magnetic properties (magnetic permeability and coercivity) of the magnetic flux collecting ring is reduced, and the permeability is reduced. The sensor sensitivity improves, the increase in coercive force decreases, and the hysteresis (history phenomenon) can be reduced.

Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.
(Embodiment 1)
FIG. 1 is an explanatory view showing a configuration of a torque detection device according to a first embodiment of the present invention, where (a) is an exploded perspective view, (b) is a longitudinal sectional view, and (c) is a transverse sectional view. . In this torque detector, an input shaft 1 (first shaft) and an output shaft 2 (second shaft) are coaxially connected via a small-diameter torsion bar 3 (connecting shaft). The input shaft 1 and the output shaft 2 are connected to the torsion bar 3 by pins 9 respectively.

A cylindrical (24 pole) permanent magnet 5 having 24 poles (12 poles each of N and S poles) magnetized at equal intervals in the circumferential direction is fixed coaxially on the input shaft 1. A cylindrical yoke 4 surrounding the permanent magnet 5 with an appropriate gap in the radial direction is fixed coaxially to the output shaft 2. As shown in FIG. 2, the yoke 4 includes two magnetic yokes 4a in which twelve isosceles triangular claws 10 extending in one direction perpendicular to the plate surface are provided at equal intervals on a plate-shaped ring. , 4b (soft magnetic material). The two magnetic yokes 4a and 4b are molded into a cylindrical shape with a synthetic resin 24 in a state in which the claws 10 face each other so as to be displaced at an appropriate interval in the circumferential direction.
Further, the magnetic yokes 4 a and 4 b are arranged in a neutral state where no torque is applied so that the tips of the respective claws 10 point to the boundary between the N pole and the S pole of the permanent magnet 5.

  The torque detection device further includes two magnetic flux collecting rings 8 and 8 (auxiliary soft magnetic bodies) that are magnetically coupled to the magnetic yokes 4a and 4b, respectively, and that induce magnetic fluxes from the magnetic yokes 4a and 4b, respectively. As shown in FIG. 2, the magnetism collecting rings 8 and 8 are arranged in parallel and have flat plate-like portions closer to each other, and one or more Hall ICs 6 are inserted into the gaps between the adjacent portions. Has been.

  The magnetism collecting rings 8 and 8 and the Hall IC 6 are molded and integrated with the synthetic resin 28 in the state described above. However, the synthetic resin 28 is provided with a plurality of holes 18, 18 to reduce the contact area between the magnetic flux collecting rings 8, 8 and the synthetic resin 28, and the magnetic flux collecting rings 8, 8 due to volume changes when the synthetic resin 28 is cured. The stress (strain) generated in the magnetism collecting rings 8 and 8 is reduced by reducing the load (pressure) on the magnet.

  FIG. 3 is a longitudinal sectional view showing a configuration example when the torque detection device having the above-described configuration is mounted on an electric power steering device. In this electric power steering apparatus, the input shaft 1 is connected to a steering (handle) (not shown), the upper half of the torsion bar 3 is loosely fitted in the hollow portion of the input shaft 1, and the upper end portion of the torsion bar 3 is pin 9a. To the input shaft 1. The lower half portion of the torsion bar 3 is loosely fitted in the hollow portion of the output shaft 2, the lower end portion of the torsion bar 3 is connected to the output shaft 2 by a pin 9b, and the input shaft is disposed above the hollow portion of the output shaft 2. The lower part of 1 is loosely fitted. The output shaft 2 is connected to a steering mechanism (not shown).

The input shaft 1 is rotatably supported by the housing 17 of the electric power steering apparatus by the bearing 13, and the output shaft 2 is rotatably supported by the housing 17 by the bearings 11 and 12.
A worm wheel 15 is fixed to the output shaft 2, and a worm 14 connected to a motor shaft of a steering assist motor (not shown) is engaged with the worm wheel 15.

  A permanent magnet 5 is coaxially fixed to the input shaft 1, and two magnetic yokes 4 a and 4 b surrounding the permanent magnet 5 with a suitable gap in the radial direction are fixed to the output shaft 2 coaxially. Yes. Around the magnetic yokes 4a and 4b, there are disposed two magnetic flux collecting rings 8 and 8 that are magnetically coupled to the magnetic yokes 4a and 4b, respectively, and are arranged in parallel at equal intervals. Two Hall ICs 6 are inserted between the adjacent flat portions of the magnetism collecting rings 8 and 8.

The magnetic yokes 4a and 4b are integrally molded with a synthetic resin 24, the magnetism collecting rings 8 and 8 and the two Hall ICs 6 are integrally molded with a synthetic resin 28. The synthetic resin 28 is a housing 17 of the electric power steering device. It is fixed to. However, the synthetic resin 28 is provided with a plurality of holes 18 to reduce the stress and strain generated in the magnetism collecting rings 8 and 8 due to the load (pressure) from the synthetic resin 28.
In the Hall IC 6, each lead wire 7 is soldered to the substrate 16, and the substrate 16 supplies power for operating the Hall IC 6 to obtain an output detected by the Hall IC 6.

  Below, operation | movement of the torque detection apparatus of such a structure is demonstrated. When no torque is applied to the input shaft 1 or the output shaft 2, the claws 10 of the magnetic yokes 4a and 4b have an area facing the N pole and S pole of the permanent magnet 5, as shown in FIG. Since the magnetic flux entering from the N pole is equal to the magnetic flux exiting from the S pole, no magnetic flux is generated between the magnetic yoke 4a and the magnetic yoke 4b.

  When a one-way torque is applied to the input shaft 1 or the output shaft 2, the torsion bar 3 is twisted, and the relative positions of the claws 10 and the permanent magnets 5 of the magnetic yokes 4a and 4b change. At this time, for example, as shown in FIG. 4A, the area of the magnetic yoke 4a facing the claws 10 is larger in the N pole of the permanent magnet 5 than in the S pole, and the magnetic flux entering from the N pole Becomes larger than the magnetic flux that goes out to the south pole. Further, the area of the magnetic yoke 4b facing the claws 10 is smaller in the N pole of the permanent magnet 5 than in the S pole, and the magnetic flux entering from the N pole is smaller than the magnetic flux exiting to the S pole. As a result, a magnetic flux is generated from the magnetic yoke 4a to the magnetic yoke 4b, and this magnetic flux density increases as the difference in area between the N pole and the S pole facing each claw 10 increases.

  On the other hand, when a torque in the other direction is applied to the input shaft 1 or the output shaft 2, the torsion bar 3 is twisted in the opposite direction to the above, and the claws 10 of the magnetic yokes 4a and 4b and the permanent magnet 5 The relative position changes. At this time, for example, as shown in FIG. 4C, the area of the magnetic yoke 4a facing the claws 10 is smaller in the N pole of the permanent magnet 5 than in the S pole, and the magnetic flux entering from the N pole Becomes smaller than the magnetic flux exiting the S pole. In addition, the area of the magnetic yoke 4b facing each claw 10 is larger in the N pole of the permanent magnet 5 than in the S pole, and the magnetic flux entering from the N pole is larger than the magnetic flux exiting to the S pole. As a result, a magnetic flux is generated from the magnetic yoke 4b to the magnetic yoke 4a, and this magnetic flux density increases as the difference in the area between the N pole and the S pole facing each claw 10 increases.

  The change in the magnetic flux density generated in the gap between the magnetic yoke 4a and the magnetic yoke 4b described above is represented by the electric angle −180 to 180 deg. If it is illustrated corresponding to (mechanical angle-15 to 15 deg.), It becomes a sine wave shape as shown in FIG. The range actually used is -90 to 90 deg. From the rigidity of the torsion bar 3. Never exceed.

  In accordance with the magnetic flux density of the gap between the magnetic yoke 4a and the magnetic yoke 4b described above, the magnetic flux generated in the magnetic yokes 4a and 4b is induced by the magnetic flux collecting rings 8 and 8, respectively. 8 and 8 are concentrated on the portions adjacent to each other and detected by the Hall ICs 6 and 6. The magnetic flux collecting rings 8 and 8 allow the Hall ICs 6 and 6 to detect the average of the magnetic flux density generated on the entire circumference of the magnetic yokes 4a and 4b.

  As described above, the Hall ICs 6 and 6 can detect the magnetic flux density according to the magnetic flux generated in the magnetic flux collecting rings 8 and 8, that is, the magnetic flux density according to the torque applied to the input shaft 1 or the output shaft 2. I can do it. That is, the applied torque can be known based on the detected magnetic flux density. In particular, by reversing the detection direction of the Hall ICs 6 and 6 and obtaining the difference between the outputs, the influences of the swinging, temperature characteristics of the Hall ICs 6 and 6 and the detection sensitivity in the axial direction can be offset and detected. Accuracy can be increased.

(Embodiment 2)
FIG. 5 is an explanatory view showing the configuration of the torque detection device according to the second embodiment of the present invention, where (a) is an exploded perspective view, (b) is a longitudinal sectional view, and (c) is a transverse sectional view. . In this torque detection device, the plurality of holes 18 of the synthetic resin 28 of the first embodiment are further enlarged to form a rectangular hole 19, and the synthetic resin 28a includes the magnetism collecting rings 8 and 8 and the two Hall ICs 6. It consists only of the parts necessary for integration.

  As a result, the contact area between the magnetism collecting rings 8 and 8 and the synthetic resin 28a is further reduced, and the load (pressure) applied to the magnetism collecting rings 8 and 8 due to the volume change when the synthetic resin 28a is cured is further reduced. The stress and strain generated in the magnetic rings 8 and 8 can be further reduced. Other configurations and operations are the same as the configurations and operations of the torque detection apparatus described in the first embodiment, and thus description thereof is omitted.

(Embodiment 3)
6A and 6B are explanatory views showing the configuration of the third embodiment of the torque detector according to the present invention, wherein FIG. 6A is an exploded perspective view, FIG. 6B is a longitudinal sectional view, and FIG. 6C is a transverse sectional view. . In this torque detection device, the magnetism collecting rings 8 and 8 and the two Hall ICs 6 are not molded and integrated with a synthetic resin as in the first and second embodiments, but the magnetism collecting rings 8a and 8a and the two magnets are integrated. First, a synthetic resin 28b (case) is formed into a shape that allows the Hall IC 6 to be fitted therein. At this time, the two Hall ICs 6 can be molded integrally with the synthetic resin 28b, or can be fitted after the molding of the synthetic resin 28b.

  As shown in FIG. 7, the magnetism collecting rings 8a and 8a are cut at the portions 20 and 20 facing the portion sandwiching the Hall IC 6, and when the magnetism collecting rings 8a and 8a are fitted into the synthetic resin 28b, The magnetism collecting rings 8a and 8a are contracted and made smaller by bringing the ends of the portions 20 and 20 closer or overlapping. The magnetism collecting rings 8a and 8a are restored to their original shapes when fitted in the synthetic resin 28b, and hardly cause stress and distortion. If the distance between both ends of the cut portions 20 and 20 is about 1 mm, the magnetic characteristics of the magnetism collecting rings 8a and 8a are the same as when the cut portions 20 and 20 are not cut.

  Further, in place of the magnetism collecting rings 8a and 8a having the cut portions 20 and 20, the magnetism collecting rings 8b and 8b having the corrugated portion 21 as shown in FIG. It is possible to fit in. Other configurations and operations are the same as the configurations and operations of the torque detection apparatus described in the first embodiment, and thus description thereof is omitted.

It is explanatory drawing which shows the structure of embodiment of the torque detection apparatus which concerns on this invention. It is a disassembled perspective view which shows the example of the magnetic yoke of the torque detection apparatus shown in FIG. 1, and a magnetism collection ring. It is a longitudinal cross-sectional view which shows the structural example at the time of mounting the torque detection apparatus based on this invention in the electric power steering apparatus. It is explanatory drawing which shows the operation example of the torque detection apparatus which concerns on this invention. It is explanatory drawing which shows the structure of embodiment of the torque detection apparatus which concerns on this invention. It is explanatory drawing which shows the structure of embodiment of the torque detection apparatus which concerns on this invention. It is a disassembled perspective view which shows the example of the magnetic yoke of the torque detection apparatus shown in FIG. 6, and a magnetism collection ring. It is a disassembled perspective view which shows the example of the other magnetic yoke and magnetism collection ring of the torque detection apparatus shown in FIG. It is a characteristic view which shows the example of the magnetic characteristic of a permalloy.

Explanation of symbols

1 Input shaft (first axis)
2 Output shaft (second shaft)
3 Torsion bar (connection shaft)
4a, 4b Magnetic yoke (soft magnetic material)
5 Permanent magnet 6 Hall IC (Hall element, detector)
7 Lead wire 8, 8a, 8b Magnetic flux collecting ring (auxiliary soft magnetic material)
10 Claw 18, 19 Hole 20 Cut-out portion (of magnetic flux collecting ring) 21 Corrugated portion (of magnetic flux collecting ring) 24, 28, 28a Synthetic resin 28b Synthetic resin (case)

Claims (2)

A first shaft and a second shaft connected coaxially by a connecting shaft, a permanent magnet fixed to the first shaft, and a magnetic circuit fixed to the second shaft and disposed in the magnetic field of the permanent magnet , A plurality of auxiliary soft magnetic bodies that are magnetically coupled to the soft magnetic body and induce magnetic flux from the soft magnetic body, and a detection that detects the magnetic flux induced by the auxiliary soft magnetic body The plurality of auxiliary soft magnetic bodies and the detector are molded and integrated with synthetic resin, and when torque is applied to the first shaft or the second shaft, the output of the detector is obtained. A torque detecting device for detecting the torque based on:
The synthetic resin includes a plurality of holes, and the torque generated in the auxiliary soft magnetic body by a mold is reduced by the holes. A first shaft and a second shaft connected coaxially by a connecting shaft; a permanent magnet fixed to the first shaft; and a magnetic circuit fixed to the second shaft and disposed in a magnetic field of the permanent magnet. , A plurality of auxiliary soft magnetic bodies that are magnetically coupled to the soft magnetic body and induce magnetic flux from the soft magnetic body, and a detection that detects the magnetic flux induced by the auxiliary soft magnetic body A torque detector that detects the torque based on the output of the detector when torque is applied to the first shaft or the second shaft.
A case made of a synthetic resin that houses the auxiliary soft magnetic body and the detector is provided, the auxiliary soft magnetic body has elasticity, and the auxiliary soft magnetic body is expanded and contracted by the elasticity and fitted into the case. Torque detection device characterized by the above.

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